Four Britons held in US custody at Guantanamo Bay, have been returned to Britain and freed without charge.

Moazzam Begg, 36, from Birmingham, Feroz Abbasi, 24, Richard Belmar, 25, and Martin Mubanga, 32, all from London, were detained at the military camp for nearly three years.

Five other Britons were returned to the UK in March 2004 and also released.

BBC News looks at the issues surrounding the Britons' detention.

More than 500 terror suspects are being held at Guantanamo Bay

How did the government help the four detainees most recently released?

Foreign Secretary Jack Straw said the US had agreed to free the remaining four British detainees after "intensive and complex discussions" over security.

He said the government had been negotiating the return of the detainees since 2003. Downing Street previously said it had pushed for their return and Prime Minister Tony Blair made a direct request to President Bush.

Talks on the detainees had taken place at many levels of the British and American governments, the Downing Street spokesman said.

But in July last year, Mr Blair said the US was not being "unreasonable" in refusing to release the last Britons at Guantanamo Bay.

He said that he was not sure the security "machinery" was in place in the UK to ensure the men posed no threat.

What was Lord Goldsmith's role?

Attorney General Lord Goldsmith, the government's top lawyer, led the negotiations to free the detainees.

The attorney general led negotiations to free the British detainees

"I have personally worked hard on that issue and no-one, perhaps apart from the prime minister, is as anxious as I am to see the position resolved," Lord Goldsmith told the BBC.

Last year Lord Goldsmith voiced concern over the planned US military trials of suspects.

He said the tribunals were unacceptable as they would not offer a fair trial.

He said the right balance must be struck between security and individual freedoms in the fight against terror. He also argued there can be "no compromise" on certain principles.

Lord Goldsmith and Jack Straw said the US should try detainees in accordance with international standards or return them.

What are the claims against the four?

Two suspects are said to have trained with al-Qaeda in Afghanistan and escaped US forces by going to Pakistan.

A third is said to have trained with al-Qaeda, met Osama bin Laden and volunteered for suicide missions.

It is said suspect four also trained at an al-Qaeda camp and scouted the derelict UK Embassy in Kabul as a possible base.

The US says he was carrying a list of Jewish groups in New York when caught.

It is understood UK police have been given dossiers on each of the men which were compiled by agents from the UK's security service MI5 who had visited them nine times at Guantanamo.

Why were military trials planned?

Former detainee Jamal Udeen alleged he was tortured in Cuba

President Bush announced plans for the military commissions to try 600 detainees at Camp Delta in 2003.

The trials were in line with the US decision not to give Guantanamo Bay detainees Prisoner of War legal status.

Feroz Abbasi and Moazzam Begg were believed to be two of six men to face the tribunals first.

However, in July 2003, the US agreed to suspend the threat of secret military hearings against the British detainees, pending talks between the two nations.

The US held the first of its military tribunals for detainees in July last year.

Why were the other five British detainees released in 2004?

Mr Blunkett visited the US last year

The move was probably tied in with a visit to the US by the then home secretary David Blunkett.

It allowed the British government to show a result from months of negotiations with the Americans.

The US also gave details of the claims against the remaining detainees for the first time, as David Blunkett arrived.

Mr Blunkett promised to push for the release of those detainees on the trip.

What happened to the released detainees?

The first five men to be released were flown back to Britain in March 2004 and questioned at London's Paddington Green police station.

All were quickly released without charge.

Four of the group launched a lawsuit against the US government in October 2004.

In the first action of its kind, Shafiq Rasul, Asif Iqbal, Ruhal Ahmed and Jamal al-Harith each demanded £5.5m, alleging torture and other human rights violations.

A Pentagon official said the allegations are false and the men are not entitled to a payout because they were captured "in combat".

What happened to the latest detainees to be returned home?

After arriving at RAF Northolt, the men were arrested under the Terrorism Act 2000 and taken to London's Paddington Green Police station for questioning.

All four were released without charge the following day and reunited with their families.